1. Field of the Invention
The present invention relates to a system and method for controlling an engine in a vehicle.
2. Background Art
The development of hybrid electric vehicles (HEV's) has provided a way to reduce exhaust emissions and improve fuel economy by reducing the amount of time an engine is running. In addition, because HEV's are equipped with electric motors, the size of the engine can be reduced. Even in some conventional vehicles, engines may be smaller today than in comparable predecessor vehicles, since advances in engine technology have provided increases in engine output power.
One consequence of having a smaller engine in a vehicle is that it may take longer for the vehicle passenger compartment to get warm. This can affect passenger comfort and convenience, in that it may also take longer for a windshield to defrost. One attempt to address this issue is described in U.S. Patent Application Publication No. 2003/0101961, published on Jun. 5, 2003 (Foster). Foster describes deactivating cylinders in an engine to increase the heat rejected to the engine cooling system. Foster also discusses reducing the cooling system heat capacity such that the engine coolant that flows through the passenger compartment heating system only flows through the engine past activated cylinders.
One limitation of the method described in Foster, is that it does not take advantage of selective use of a charge motion control valve. These valves are used on some engines to increase the turbulence of the intake air entering the engine, thereby increasing the efficiency of combustion. When a charge motion control valve is opened, the amount of intake air entering the engine is increased; this is normally associated with cooler combustion. The opening of a charge motion control valve also decreases the turbulence of the intake air entering the engine, however, which can counter the effects of the increased amount of air, and lead to an increase in the combustion temperature. This, in turn, can help to more quickly heat the passenger compartment.
Another situation that can undesirably increase the time it takes to heat a passenger compartment is execution of a control logic configured to quickly heat a catalyst after the engine is started. Such a control logic may be used to reduce undesirable exhaust emissions, but may have the unintended effect of making less heat available to the passenger compartment. One method that has been used to quickly heat a catalyst is to severely retard the spark timing in a spark ignition engine. This causes unburned fuel that is exhausted from the engine to be combusted at or near the catalyst itself. Although this provides a method for quickly heating the catalyst, it reduces the amount of heat that can be transferred to an engine coolant, and ultimately transferred to the vehicle passenger compartment. Therefore, merely retarding spark timing, and in particular retarding it past top dead center (TDC), can be at odds with quickly heating a vehicle passenger compartment.
Therefore, a need exists for a system and method to utilize various vehicle adjustments to facilitate a more rapid heat transfer from the engine to the vehicle passenger compartment.